TESORO GOLDEN SABRE

[Max]

Hi all,
found another difference from schematic to PCB !

How many! Why ? Who knows ?... but it works good... so nevermind!

Difference is:

in schematic between pins 6 and 7 of LF353: cap =10pF
in PCB same cap is instead =5pF

Kind regards,
Max

Here is the map of misteries...

[nelson]

MAX, WHAT YOU CAN GET IF YOU CHANGE THIS COMPONENTS HAS IS SHOW ON THE SCHEMATIC AND NOT THE PCB?
ALSO, I UNDERSTAND THAT GOOD RESULTS OBTEINED BY YOU AND IVCONIC ARE WITH COMPONENTS SHOW ON PCB SCKETCH, RIGTH?, CAUSE I DON´T WANT TO BE CONFUSED AFTER I FINISH MY 22 CMS COIL, SO BY NOW I HAVE PLAN TO DO MY TEST WITH THE ORIGINAL PCB SET UP.

REGARDS

NELSON

Hi all,
found another difference from schematic to PCB !

How many! Why ? Who knows ?... but it works good... so nevermind!

Difference is:

in schematic between pins 6 and 7 of LF353: cap =10pF
in PCB same cap is instead =5pF

Kind regards,
Max

Here is the map of misteries...

[tiktak]

Hi

Hi,
Max.
I think that I reach around 26 cm with unshielded coils.
The sound is from 8 ohm speaker/I now its no good,but..../!
But when you detect there are terains that dont alaud to keep search head close to the ground,so this is not so good result.
But its more than many expencive toys!'
I will try to achive better results.

[Max]

MAX, WHAT YOU CAN GET IF YOU CHANGE THIS COMPONENTS HAS IS SHOW ON THE SCHEMATIC AND NOT THE PCB?
ALSO, I UNDERSTAND THAT GOOD RESULTS OBTEINED BY YOU AND IVCONIC ARE WITH COMPONENTS SHOW ON PCB SCKETCH, RIGTH?, CAUSE I DON´T WANT TO BE CONFUSED AFTER I FINISH MY 22 CMS COIL, SO BY NOW I HAVE PLAN TO DO MY TEST WITH THE ORIGINAL PCB SET UP.

REGARDS

NELSON

Hi Nelson,
I've done modifications of component list as indicated in an above post.
But just for active devices and some spare:
- 4xBF244B in middle section (sampler) instead of BF245C (changed pinout of to-92)
- 2xBF245C in battery checker and osc section
- 1xLF353 as preamp (but tested others)
- used 2N3904/2N3906 instead of 2N2222/2N2907
- 1xTLC2262 instead of TL062
- 1xC517 (not BC, but it's the same stuff, pinout etc)
- 1x8ohm speaker

+ 2xTL081 instead of LM308

Just these of above, not resistors or caps or diodes. I followed the PCB labels, so mounted e.g. 5pF between pin 6 and 7 of 353, not 10pF as in schematic.

Change e.g. of fets or bip.-transistors if not a big change really. About same thing. LF353 as preamp. as described, and just 3 IC mod (tlc2262 instead of tl062, 2xtl081).

So don't worry. About the same.

Best regards,
Max

[Max]

Hi,
Max.
I think that I reach around 26 cm with unshielded coils.
The sound is from 8 ohm speaker/I now its no good,but..../!
But when you detect there are terains that dont alaud to keep search head close to the ground,so this is not so good result.
But its more than many expencive toys!'
I will try to achive better results.

Well done. Keep tuning now.

[Max]

Hi,
I think that there are just few relevant things in that differences I described in the schematic using green color.

I think most important is that capacitor between pin6 and 6 of 353.

If you change values of this you have different freq. response of preamp.

I've mounted 5pF, like in PCB-chart, but I'm a bit puzzled and think that maybe correct values is 10pF for it. I'm not sure... of that, and also side effects could be really small for real.

But I think it is in a really "hot spot".

Also the 33k resistor that is 2K2 in PCB is not a real "error".

What to say... maybe it was 10pF ! But my detector works fine with 5pF!
So I'm not worried too much of this...

I'll check it, anyway, in next days.

Another funny thing is the 470ohm in schematic that become 470K in PCB,
at battery checker.

Best regards,
Max

PS: a big mistake was the 150pF cap ! But already corrected much time ago.

[Max]

Hi,
yo make things more clear, the differences you see:

- red : what I consider real mistakes, that could affect circuit working (or part of it working as expected e.g. battery checker)
- green : just a mod. for tuning and not really a mistake

Some mistakes are in schematic only, like 150pF and resistor connection to diode, or 47K resistors... others are in PCB (e.g. 5pF instead of 10pF) but I've indicated in schematic to have a reference there.

Best regards,
Max

[Max]

where they are... on the PCB

[nakky]

sound

Hi Nelson,
I've some 50 ne5532... tested there and it's not good (for me) as replacement this time, at least for my taste: lose many performances... and TL072 is better than it this time.

I have NE5532 originals by Philips.

If you have dubts, buy one and see with your eyes.
Very easy to find and cheap.

What I'm talking about is not just related to noise at preamp. but have more to do with input stage of op. amp. that is a very tipical fingerprint expecially for jfet inputs op. amp.

That's why I've indicated the analog and TI replacements.

I've tested 566 circuit (the one you can see in Sasho's thread, with bc547 and bc557, but arrows are in wrong places... anyway) I'm not so happy of results... get sound and VCO operations, of course, but sound it's not loud as I want. Think that a TBA820M could solve any problem of loudness.

Yes, LM566 is almost impossible to find. My new 3 pieces were from an old 80's stock. I'm sure somewhere is possible to find it from old stocks unselled products, but it's a hard challenge not for anyone to get this stuff.

Best regards,
Max

Hi Max,play with the 33K for sound.Grt Nakky.

[Max]

Hi Max,play with the 33K for sound.Grt Nakky.

Hi Nakky,
yes is on my "list" ! This set the gain of last stage. Also the darlington gain is another good issue. Actually I have instead of 33K as in schematic, the 2K2 value as in PCB diagram. Think that 1Kohm could be better.

Other thoughts are:

I was thinking just avoid the C517 and wire a small audio amplifier like Leto have done before. A TBA820M (1.2W, low quiescent current , audio amp.) could solve some of the problems related to weak audio in a good way I think: it don't waste energy (just few mA) when no sound, then get really an audio boost when I need sound (1.2 W is a convenient power for e.g. a small 8ohm speaker), thus resolving also the impeadance problem.

Of course, no VCO that way, but if one need VCO, could wire between circuit and tba820m an LM566, like Ivconic have done, then getting the audio power from the TBA820M.

Best regards,
Max

[Max]

REVISED FULL SCHEMATIC

Hi,
I've changed the wrong values and revised full schematic, according also to the "GSabre light" values.

If someone will find any new error or mistake, please post here.

Kind regards,
Max

[Max]

About the 33K resistor and all the story

Hi all,
I've replaced the 2K2 resistor with the 33K that is indicated in schematics and lose some audio! (as expected)

Just small beeps when coin is near 26-27cm from center of coil... almost weak and unuseful... and one could miss much targets that way.

The gain reduction is not good if you want detect stuff at depth.

Then unsatisfied of result I've put a 1K resistor instead of that 33K... and wow it's singing BUT there is some small instability due the too high gain.

So I remounted the 2K2 as in the PCB drawing.

I think that the 1K is ideal if you can keep detector stable (somehow) and avoid bleeping.

The AD712 could save the day but I haven't ! And can't test.

I think that I gained 2cm with 1K instead of 2K2...
then mounted NE5532 instead of LF353 but lose some depth (1-2cms)!
With again LF353 too bleeping convinced me remount the 2K2, at least for now.

BTW changed also the 5pF cap with 10pF... and results are the same.
So no need to change it at preamp (LF353).

Best regards,
Max

[tiktak]

Hi,

Hi,
Max.
What you think about CA3240 insted of 353 or:LM358D ;LM2904 ;LM258N?
Plese help!
I will have 353 after 2 weeks!

[Max]

Hi,
Max.
What you think about CA3240 insted of 353 or:LM358D ;LM2904 ;LM258N ?
Plese help!
I will have 353 after 2 weeks!

Hi tiktak,
I think positive of it (CA3240) cause seems good.

1.5TΩ mosfet inputs... seems fine. Problem is that you have to test in circuit to say that's better than TL072.
Other things for me aren't so good, btw 158/258/358 are about the same stuff.
LM2904 seems about a step above 358, no good here.

I get less bleeping with NE5532 but lose performances... (probably cause of input stages) so I think your CA3240 could be good alternative for 353.

Buy one and test.

Kind regards,
Max

PS:
Not too seem too techical but... from what I see seems good as inputs, very good (look at Q9, Q10 config).
I think would be nice instead of 353.

[tiktak]

Hi,

Thanks.
I think that have one.Will see.
And will tell you.